The present invention relates to control valves and in particular, to an evaporative (EVAP) solenoid control valve including a plunger having noise reduction features.
It is known in the art of automotive fuel systems to use an evaporative (EVAP) solenoid valve assembly to control the flow of fuel vapor through passageways connecting a purge canister and an intake manifold. One such EVAP control valve assembly includes a solenoid assembly actuated in response to a pulse width modulated (PWM) signal generated by the vehicle""s central computer to induce a plunger to move toward a metal stop, opening a passageway to the flow of vapor. When the solenoid is de-energized, the plunger is pushed back toward a valve seat by a pre-loaded spring situated between the stop and the plunger, causing the plunger to seal the passageway.
The force of impact as a result of the plunger striking the valve stop or seat has been known to generate noise in some applications. Accordingly, EVAP control valve plungers have been designed to include a soft, rubber-like stop cushion at the interface with the valve stop and a rubber tip for sealing against the valve seat. At room temperature, noise due to impact with the stop or seat may be maintained at relatively low levels since the soft portions of the plunger exhibit relatively large deflection during impact, absorbing large amounts of the impact energy and extending the impact time to reduce the average impact force. However, where temperatures are close to or below the glass transition temperature of some kinds of rubber, those kinds of rubber tend to harden which may reduce the noise-dampening attributes.
The present invention provides an evaporative control valve including a plunger reciprocable between a valve stop and a valve seat to open and close a controlled port. The plunger has a body, a flexible support member mounted on one end of the body and a resilient tip positioned on the support member for sealing engagement with the valve seat. When the resilient tip of the plunger impacts the valve seat, the flexible support member absorbs substantially all of the force of impact by deflecting in the direction opposite the plunger movement, increasing impact time and reducing noise which may be generated. According to a further feature of this invention, the resilient tip may be positioned on the flexible support member to further define a stop cushion to further reduce impact of the plunger against the valve stop.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings and appended claims.